This invention relates to pneumatic tires and in particular to pneumatic tires in which the tread portion thereof includes fabric reinforcement.
The tread portions of many pneumatic tires, belted or non-belted, are essentially free of fabric reinforcement.
However, many of the so-called "high speed" pneumatic tires, such as, for example, aircraft tires, employ a layer of fabric or cords which reinforce the tread portions thereof. The advantages achieved by and typical details of such fabric reinforced tire treads are described in U.S. Pat. No. 2,943,663, assigned to the same assignee as the present invention.
The building of fabric reinforced tread portions is time consuming and tedious due to the fact that such tread portions comprise at least three distinct annular layers or zones each of which can require several building steps. Normally, such tread portions include a radially inner, circumferentially disposed "inner" or "under" tread layer or zone of essentially fabric-free elastomeric material, a radially intermediate circumferentially disposed layer of fabric-reinforced elastomeric material and a radially outer, circumferentially disposed "outer" tread layer of essentially fabric-free elastomeric material. Building of the radially intermediate layer is usually the most difficult because said layer is usually composed of one or more sheets or plies of rubberized fabric or cords, the widths thereof generally corresponding to the width of the outer and/or inner tread layer. When retreading these tires generally the same application steps are required as were required in building the original tread.
Because of the wide range of tire sizes which can require a reinforced tread portion, wide varieties of sizes of inner and outer tread layers as well as reinforcement layers must be available to a tire builder or retreader. This can represent inventory and storage problems as well as time consuming cutting and sizing of one or more of the components used.
In recent years these problems have been somewhat alleviated by what are generally termed "strip-treading" techniques in which cord-free tread portions or layers are formed by wrapping or winding a narrow strip of elastomeric material around the tire circumference in a plurality of overlapping turns. A typical description of this technique appears in U.S. Pat. No. 3,177,918.
When building fabric or cord reinforced tire tread portions, however, there still remains the necessity that the radially intermediate layer be formed by wrapping one or more specifically sized sheets of rubberized cord or fabric plies prior to forming at least the outer tread layer by strip winding.
There have been attempts at strip winding tread portions with cord reinforcement wherein one or more cords are put in an elastomeric strip and wound simultaneously with the strip on the tire to form the tread portion. (See, for example, U.S. Pat. No. 3,607,497).
Techniques such as this, however, do not permit a variation in the amount of fabric or cord used in a given reinforcement layer design because the design and amount of fabric or cord laid down is dictated by an already determined contour or amount of the outer tread layer material.